Hi I would just try (e.g.) '1' for one voxel size and '2' for the
other, and then demean that EV. Cheers
--------------------
Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington,
Oxford. OX3 9 DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask]
http://www.fmrib.ox.ac.uk/~steve
----------------------
On 23 Dec 2008, at 13:41, "Erick Canales Rodriguez (Benito Menni
CASM)" <[log in to unmask]> wrote:
> Hi Steve,
>
> Thanks for your reply,
> In your opinion the spatial resolution of the data can be considered
> as a covariable in the general linear model?
> For example, one additional column (EV) to include the volume of the
> voxel.
>
> Best regards,
>
> Erick J. Canales-Rodríguez
>
> (+34) 93 652 99 99 ext. 255
>
> Unitat de Recerca, Benito Menni CASM (http://www.hospitalbenitomenni.org/Default.aspx
> )
> Sant Boi del Llobregat (Barcelona), Espanya/España/Spain
>
> Benito Menni Complex assistencial en Salut Mental
> ________________________________________
> De: FSL - FMRIB's Software Library [[log in to unmask]] En nombre de
> Steve Smith [[log in to unmask]]
> Enviado el: martes, 23 de diciembre de 2008 14:02
> Para: [log in to unmask]
> Asunto: Re: [FSL] TBSS with different diffusion data?
>
> Hi,
>
> See previous posts on this: in general people are very wary of trying
> to combine data across different protocols. You will have a bias in
> pretty much all diffusion-derived measures, which may not be trivally
> modellable, and is almost certainly not solvable by re-interpolating
> your data, sadly. However, IF you put in the protocol labelling as a
> confound regressor to randomise, and IF your regressors of interest do
> not correlate strongly with this, and IF your data is well matched
> across the protocol groups, then you might get away with this........
>
> Cheers.
>
>
>
> On 23 Dec 2008, at 10:33, Erick Canales Rodriguez (Benito Menni CASM)
> wrote:
>
>> Hello FSL,
>>
>> My interest is to compare two groups of subjects with TBSS, however,
>> the diffusion MRI data corresponding to each group was recorded with
>> a different spatial resolution (in the same MRI machine). That is,
>> the same b-value and diffusion gradient directions but different
>> voxel size, the first group: 1.13x1.13x5 mm and the second one:
>> 0.94x0.94x5 mm.
>> My question is, it is possible to use TBSS to infer FA differences
>> in groups with data at different spatial resolutions? Typically this
>> procedure is not a good practice, however, I consider this
>> possibility due to the data was measured with a resolution lower
>> than the resolution of the template used in TBSS: 1x1x1 mm.
>> A possible solution may be to interpolate the resulting FA images to
>> the same spatial resolution prior to the TBSS analysis. A second
>> variant may be to perform the interpolation directly on the measured
>> diffusion data. There is any script in FSL to perform accurately
>> these interpolations?
>> Many thanks in advance,
>>
>> Erick J. Canales-Rodríguez
>>
>> (+34) 93 652 99 99 ext. 255
>>
>> Unitat de Recerca, Benito Menni CASM (http://www.hospitalbenitomenni.org/Default.aspx
>> )
>> Sant Boi del Llobregat (Barcelona), Espanya/España/Spain
>>
>> Benito Menni Complex assistencial en Salut Mental
>> ________________________________________
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